This invention relates to monitoring the proliferation of migratory cells such as CNS stem cells/embryonic stem cells or any other migratory cells. More specifically, an apparatus and process is disclosed for placing isolated islands of an extracellular matrix on a glass cover slip, and, plating, growing, and monitoring the proliferation of migratory cells on the isolated islands of the extracellular matrix.
Migratory cells, such as CNS stem cells/embryonic stem cells or any other migratory cells are grown and simultaneously monitored during proliferation for research purposes. Typically, an extracellular matrix is placed upon a substrate, usually a coverslip. Thereafter, cells are plated to (placed on) the extracellular matrix for observation during proliferation. During this observed proliferation, the cells unfortunately also migrate.
Migration causes problems. Typically, only a discrete area on a substrate, such as a portion of a substrate having the extracellular matrix, can be observed. During migration, cells within the observed discrete area move out of the observed discrete area; what becomes of such cells is never known to the observer. Other foreign cells, initially outside of the observed discrete area, move into the observed area; as a consequence, the beginning history of such cells can never be known to the observer. In either case, the integrity of the monitoring processes is degraded. Where one wishes to have an observed history of the proliferation of a group of monitored cells, migration of the cells into or out of the observed area must be inhibited.
For this reason, where cell populations are grown on substrates, such as glass cover slips, attempts have been made to provide isolated islands of substrate. These isolated islands of substrate have the effect of allowing cell migration within their boundaries while maintaining a discrete cell population within an observable area.
Attempts to create isolated islands has included printing glass cover slips with the desired isolated islands. In this technique, the material from which the extracellular matrix is ultimately formulated is placed upon a printing block having printing areas shaped with the desired profile of isolated islands of extracellular matrix. Thereafter, the printing block is impressed upon a substrate, such as a glass cover slip, to transfer the extracellular matrix material from the print block to the glass cover slip. Substrate material is transferred from the printing block onto the glass cover slip much as printer's ink is transferred from a printing block onto paper which is to be printed. The extracellular matrix transferred to the substrate has the profile of the printing areas on the printing block.
Other techniques have included photo lithographic masks utilizing photo resist, contact masks, micro stamping, and ink jet printing.
For many of these techniques to work, drying of the substrate transferred on the glass cover slip from the printing block is required. Unfortunately, drying substantially degrades or destroys the extracellular matrix. The growth of cells for subsequent observation is difficult. Further, many of these techniques leave residual chemicals (such as photo resist) with the deposited substrate. These residual chemicals degrade the subsequent growth on the substrate. Most importantly, these techniques do not permit plating of the migratory cells before formation of the islands of substrate.
It has also been contemplated to utilize lasers to form continuous channels upon a continuous layer of extracellular matrix on a glass cover slip. In this technique, the extracellular matrix is placed upon a substrate, typically a glass cover slip. Once the extracellular material is placed, at least one laser is utilized to etch channels in the extracellular matrix. Typically, the extracellular matrix is submerged during laser etching of channels. This provides isolated islands of extracellular matrix having separation between isolated islands complimentary to the channel width and placement on the substrate.
The technique suffers from several disadvantages.
Utilizing lasers to make such channels is expensive. Further, the ablation of the extracellular matrix generates debris and produces localized heating at the channel boundaries which can damage the extracellular matrix adjacent the channel boundaries. Further, if cutting of the channels occurs while the matrix is submerged in a liquid, localized heating of the substrate will occur.